The so-called thermite reaction has been used to make "bombs" that can melt through the armor plating of a tank. The components of the reaction are aluminum metal and iron oxide (rust). Finely ground powders of each are mixed together. A fair amount of heat is necessary to get the thermite reaction going, but then it really takes off, generating all the heat it needs to keep going and more. The products are aluminum oxide and, more importantly
molten iron.
Don't try this at home, kids. Instead see it from the safety of
Google Video. How hot is 2500 C? That would be 4532 F, which is pretty toasty. (H/T BillV)